Add Resiliency to the concepts page

Signed-off-by: Nick Greenfield <nigreenf@microsoft.com>

daprdocs/content/en/concepts/resiliency-concept.md

@@ -0,0 +1,29 @@
+---
+type: docs
+title: "Resiliency"
+linkTitle: "Resiliency"
+weight: 400
+description: "Configure retries, timeouts, circuit breakers and monitor app health"
+---
+
+Distributed applications are commonly comprised of many microservices, with dozens, sometimes hundreds of instances scaling across underlying infrastructure. As these distributed solutions grow in size and complexity, the potential for system failures inevitably increases. Service instances can fail or become unresponsive due to any number of issues, including hardware failures, unexpected throughput, or application lifecycle events, such as scaling out and application restarts. Designing and implementing a self-healing solution with the ability to detect, mitigate, and respond to failure is critical.
+
+## Resiliency Policies
+<img src="/images/resiliency_diagram.png" width="1200" alt="Diagram showing the resiliency applied to Dapr APIs">
+
+Dapr provides a capability for defining and applying fault tolerance resiliency policies to your application. You can define policies for following resiliency patterns:
+
+- Timeouts
+- Retries/back-offs
+- Circuit breakers
+
+These policies can be applied to any Dapr API calls and when calling components with a [resiliency spec]({{< ref resiliency-overview >}}).
+
+## App Health Checks
+<img src="/images/observability-app-health.webp" width="800" alt="Diagram showing the app health feature. Running Dapr with app health enabled causes Dapr to periodically probe the app for its health">
+
+Applications can become unresponsive for a variety of reasons, for example, they are to busy to accept new work, could have crashed, or be in a deadlock state. Sometimes the condition can be transitory or persistent.
+
+Dapr provides a capability for monitoring app health through probes that check the health of your application and react to status changes. When an unhealthy app is detected, Dapr stops accepting new work on behalf of the application.
+
+Read more on how to apply [app health checks]({{< ref app-health >}}) to your application.